We read with interest Shiraishi and coworkers' report of a patient who developed Charles Bonnet syndrome (CBS) during two distinct periods when his visual acuity was declining (Shiraishi et al. 2004). These were followed by hallucination-free periods when his visual acuity was static; in the first case, when visual acuity improved to 0.6 and, later, when the patient became blind. Therefore, it is interesting to note that although CBS is associated with poor visual acuity (Teunisse et al. 1995), the patient experienced hallucinations when his visual acuity was dropping to hand movement, yet the hallucinations ceased when he was blind. We agree with the authors that it may be the dynamic change in visual acuity and not its chronic or static level that is important in the pathogenesis of CBS (Shiraishi et al. 2004). We would now like to propose a possible pathophysiological explanation for these interesting observations, and support this proposal by discussing other patients who have exhibited a similar temporal sequence of events.
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